You can’t circumvent auto-play from being blocked. There has to be some user interaction before the audio can play. This is the same for both HTML <audio> element as well as the web-audio API’s audioContext

There’s some reading about this on MDN Autoplay guide for media and Web Audio’s API

You can try to play the audio on javascript onload.
Example:

HTML:

<audio controls id="horseAudio">
    <source src="https://www.w3schools.com/html/horse.ogg" type="audio/ogg">
    <source src="https://www.w3schools.com/html/horse.mp3" type="audio/mpeg">
    Your browser does not support the audio element.
</audio>

JavaScript:

window.onload = function (){
    document.getElementById("horseAudio").play();
}

I’m trying to add autoplaying music to a tumblr theme, but Chrome and Firefox both prevent autoplaying audio by default. How do I circumvent this?

Currently, to hear the autoplaying music, a user would have to change their personal browser settings to allow autoplay. Is there a workaround I can use to make the page play audio even if they have sound set to automatic (in Chrome) or autoplay blocked (in Firefox)?

Tumblr themes allow HTML, CSS, and Javascript, so I’d be happy for a solution using any of those. Ideally I would like my autoplay solution to allow multiple songs in a playlist, if possible.

I tried adding an invisible iframe, but that didn’t work; I’m not sure whether it was the third-party audio player I’m using, or just that the iframe technique doesn’t work at all anymore.